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pnmcut - cut a rectangle out of a PBM, PGM, or PPM image
pnmcut
[-left leftcol] [-right rightcol] [-top toprow] [-bottom bottomrow] [-width
width] [-height height] [-pad] [-verbose] [ left top width height ] [pnmfile]
All options may be abbreviated to the shortest unique prefix.
Reads
a PBM, PGM, or PPM image as input. Extracts the specified rectangle, and
produces the same kind of image as output.
There are two ways to specify
the rectangle to cut: arguments and options. Options are easier to remember
and read, more expressive, and allow you to use defaults. Arguments were
the only way available before July 2000.
If you use both options and arguments,
the two specifications get mixed in an unspecified way.
To use options,
just code any mixture of the -left, -right, -top, -bottom, -width, and -height
options. What you don't specify defaults. It is an error to overspecify,
i.e. to specify all three of -left, -right, and -width or -top, -bottom, and
-height.
To use arguments, specify all four of the left, top, width, and
height arguments. left and top have the same effect as specifying them
as the argument of a -left or -top option, respectively. width and height
have the same effect as specifying them as the argument of a -width or -height
option, respectively, where they are positive. Where they are not positive,
they have the same effect as specifying one less than the value as the
argument to a -right or -bottom option, respectively. (E.g. width = 0
makes the cut go all the way to the right edge). Before July 2000, negative
numbers were not allowed for width and height.
Input is from Standard Input
if you don't specify the input file pnmfile.
Output is to Standard Output.
- -left
- The column number of the leftmost column to be in the output.
If a nonnegative number, it refers to columns numbered from 0 at the left,
increasing to the right. If negative, it refers to columns numbered -1 at
the right, decreasing to the left.
- -right
- The column number of the rightmost
column to be in the output, numbered the same as for -left.
- -top
- The row
number of the topmost row to be in the output. If a nonnegative number
it refers to rows numbered from 0 at the top, increasing downward. If negative,
it refers to columns numbered -1 at the bottom, decreasing upward.
- -bottom
- The row number of the bottom-most row to be in the output, numbered the
same as for -top.
- -width
- The number of columns to be in the output. Must
be positive.
- -height
- The number of rows to be in the output. Must be positive.
- -pad
- If the rectangle you specify is not entirely within the input image,
pnmcut fails unless you also specify -pad. In that case, it pads the output
with black up to the edges you specify. You can use this option if you need
to have an image of certain dimensions and have an image of arbitrary dimensions.
pnmpad can also fill an image out to a specified dimension, and gives
you more explicit control over the padding.
- -verbose
- Print information about
the processing to Standard Error.
pnmcrop(1)
, pnmpad(1)
, pnmcat(1)
,
pgmslice(1)
, pnm(5)
Copyright (C) 1989 by Jef Poskanzer.
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